The present invention relates to projection screens and more particularly to a projection screen having a treated metallic aluminum substrate, as well as to a process for the production thereof.
A known type of projection screen using metallic aluminum comprises an aluminum foil layer having a pattern of directional irregularities and a plastic coating overlying the pattern; another known projection screen comprises an aluminum foil layer adhered to a glass fiber reinforced polyester backing shaped in a form of spherical surface. These known types of screens can be used for projection under daylight conditions, but suffer from disadvantages such as strong gleam in a direction normal to the screen surface which results in eye fatigue and difficult viewing. In addition, these known types of aluminum screens are subjected to the formation of wrinkles and a wavy surface upon final processing, as well as deformation and low rigidity.
When an aluminum surface is subjected to etching, or to sandblasting to form a pattern of non-directional irregularities and then anodized for use as a projection screen, the surface irregularities of the resulting screen have poor directional properties and (with particular reference to the sandblasted pattern) exhibit a non-uniformity of distribution, in a microscopic sense, which is not suitable for a projection screen necessitating high luminance.